On the extreme sterility so-called "straight head" of rice plant occurred in farmer's field of Chiba Prefectureowing to dry weather in 1947. : preliminaly report

摘要

The result of investigation is summarizee as follows; 1. The "strairght head" occurred when the soil was not dried so extremely and consequent]y plants showed no wilting and no remarkable injury as to vegetative growth. 2. The "straight head" occurred when the plants were exposed to drought at such three stages in the process of rice panicle development namely stage of differentiation of flower primordia, stage of differentiation of flovver primordia, stagl of reduction division of germ cell and also stage of heading and flowering. 3. The "straight head" occurred seriously at where the soil shows high manuring effect by drying or at where the soil is deficient in activated iron. 4. The occurrence of "straight head" was inhibited by suppling water during the period from 19 days to 12 days previous to heading and was promoted by irrigation before or after that period. 5. It was assumed that the extreme sterility occurs when the panicle or flower are able to continue their development, without ceasing, under drought condition and simultaneously there is temporal unbalance of water relation in the plant which happens during the short duration of noontime of every day resulting from acceralated transpiration at that time.